Gas turbine engines operate to produce mechanical work or thrust. Specifically, land-based gas turbine engines typically have a generator coupled thereto for the purposes of generating electricity. A gas turbine engine comprises at least a compressor section having a series of rotating compressor blades. The compressor receives air from an engine inlet. The air passes through the compressor, which causes the pressure of the air to increase. The compressed air is then directed into one or more combustors where fuel is injected into the compressed air and the mixture is ignited. The hot combustion gases are then directed from the combustion section to a turbine section by a transition duct. Depending on the geometry of the gas turbine engine, often times the combustion section is located radially outward of the inlet to the turbine section, and therefore the transition duct must change in at least a radial profile.
A change in the radial profile can cause numerous assembly issues between the combustor and the turbine. Also, such a change in geometry for the transition duct assembly, which is operating at extremely high temperatures can create high thermal and mechanical stresses in the transition duct assembly.
By nature, the transition duct assembly has a natural operating frequency. Also, the gas turbine engine has a natural frequency, and orders of the natural frequency (i.e. 1E, 2E, 3E, etc). When a component has a natural frequency that coincides with an engine natural frequency or order thereof, the component can become dynamically excited and if care is not taken to avoid the crossings of these frequencies, or minimizing the time for the crossing, the component may experience excessive wear or failure due to the excessive vibrations that occur when operating at the natural frequency or order thereof.